Grease compatible mineral oil extended polyurethane

ABSTRACT

A cured, cross-linked, mineral oil extended polyurethane which is non-spewing. The mineral oil extended polyurethane is further characterized by being grease compatible in that the tendency of the mineral oil to migrate is substantially reduced or eliminated. The mineral oil extended polyurethane is comprised of a defined polyurethane, mineral oil, and coupling agent. In other aspects, the present invention relates to a process for reclaiming or sealing an insulated electrical device and to an insulated electrical device which is formed by such process.

This is a division of application Ser. No. 877,905, filed Feb. 15, 1978,now U.S. Pat. No. 4,168,258 issued Sept. 18, 1979.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a grease compatible, cured, cross-linked,mineral oil extended polyurethane which is non-spewing, a process forreclaiming or sealing electrical devices by using the mineral oilextended polyurethane and the reclaimed or sealed electrical devicesformed by such process.

2. Description of the Prior Art

It is an established practice in the art to use a variety of materialsto extend polymers. The extension material or extender is generallyselected depending upon the desired utility of the extended polymer,such utilities including the preparation of adhesives, molded articles,construction material, flooring and a multitude of other products.

It is also known in the art to use extended polyurethanes in thepreparation of these products. One development in this field is anaromatic oil extended polyurethane. The aromatic oil extendedpolyurethane is particularly useful in the reclamation or rehabilitationof insulated electrical devices, such as underground multi-conductortelephone cables, which have been penetrated with fluid contaminantssuch as water. Compared to former techniques of reclaiming suchinsulated electrical devices, involving the injection of acetone or aninert gas, the use of aromatic oil extended polyurethane is aconsiderable improvement since it remains in the electrical device,after curing in situ, and forms a hydrophobic barrier against furtherwater and aqueous penetration.

In an analogous utility, the aromatic oil extended polyurethane may beused as an encapsulant in sealing sections of cable wherein splicing orother repairs have been performed. In this embodiment, the extendedpolyurethane is maintained in the vicinity of the splice and serves, notto displace fluid contaminants, but to prevent their penetration whenthe cable is replaced in its original position.

In either the reclamation or encapsulant utilities, a principaldisadvantage of using an aromatic oil extended polyurethane in aninsulated cable is that the aromatic oil tends to chemically attack theplastic (e.g., polycarbonate) conductor connectors and/or polyolefinsheathing which is typically present in the cable. Additionally, thearomatic oil poses considerable danger to installing personnel due toits toxic, volatile nature.

In an effort to overcome the aforementioned problems attendant with theuse of aromatic oils, the prior art attempted to extend polyurethanesusing mineral oils. These prior art systems were not entirely successfulsince the mineral oil tended to exude or "spew" from the mineral oilextended polyurethane, particularly at higher extensions, e.g., aboveabout 2:1, oil to polymer. It has also been found that extended periodsof time and colder temperatures cause this "spewing" phenomenon, even atlower extensions.

The problems of the prior art were solved or substantially reduced bythe mineral oil extended polyurethane described and claimed inapplicant's U.S. Pat. No. 4,008,197. As more fully discussed therein, anon-spewing, cured, cross-linked, mineral oil extended polyurethane isobtained via the use of a defined polyurethane and a defined couplingagent.

The non-spewing, cured, cross-linked, mineral oil extended polyurethaneof applicants' patent is particularly useful in the reclamation orencapsulation of underground cables in that it possesses excellentchemical and electrical properties. Specifically, this mineral oilextended polyurethane does not spew oil, even with oil extensions ashigh as about 10:1, to oil polymer, or over extended periods of time andat colder temperatures, and does not present a health hazard toinstalling personnel. The mineral oil extended polyurethane also doesnot chemically attack the plastic materials normally found inunderground cables. Additionally, it possesses a high insulationresistance, a high volume resistivity, a low dissipation factor and alow dielectric constant which is required in an underground cable and isrelatively low in specific gravity whereby it does not greatly increasethe weight of the reclaimed or encapsulated cable.

It has now been discovered that when the non-spewing, cured,cross-linked, mineral oil extended polyurethane described in applicants'patent is brought into contact with grease, which is often present innewer insulated electrical devices such as underground cables, themineral oil tends to migrate towards the grease. The migration causesthe formation of an oily film at the grease interface and tends todecrease the effectiveness of the mineral oil extended polyurethane inthe prevention of aqueous contamination of the electrical device.

OBJECTS AND SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a mineraloil extended polyurethane which eliminates or substantially reduces theproblems of the prior art and which is additionally compatible withgrease.

It is a more specific object of the present invention to provide agrease compatible, cured, cross-linked, mineral oil extendedpolyurethane which is non-spewing and which incorporates a specificallydefined polyurethane, mineral oil and coupling agent.

It is another object of the present invention to provide a process foremploying the grease compatible, mineral oil extended polyurethane inthe reclaiming or sealing of insulated electrical devices, andparticularly the sealing of grease containing insulated electricaldevices.

It is yet another object of the present invention to provide insulatedelectrical devices which have been reclaimed or sealed with the greasecompatible, mineral oil extended polyurethane.

These and other objects, as well as the scope, nature and utilization ofthe invention will be apparent from the following summary anddescription of the preferred embodiments of the present invention.

In one aspect, the present invention relates to a grease compatible,cured, cross-linked, mineral oil extended polyurethane which isnon-spewing. The mineral oil extended polyurethane comprises a definedpolyurethane and/or a defined mineral oil and/or a defined couplingagent, wherein at least two of the defined materials are present in eachinstance.

In an aspect of the present invention wherein the polyurethane, themineral oil and the coupling agent are all defined to obtain a reductionor elimination in mineral oil migration, the mineral oil extendedpolyurethane comprises:

(a) from about 8 to about 45 parts, by weight, of polyurethane, saidpolyurethane being prepared by reacting

(i) a polyisocyanate prepolymer with

(ii) a polyol selected from the group consisting of castor oil,polyether polyols, hydroxyl bearing homopolymers of dienes, hydroxylbearing copolymers of dienes, and combinations thereof,

(b) from about 20 to about 75 parts, by weight, of mineral oil, saidmineral oil being characterized by having from about 1.0 to about 30%aromatic carbon atoms, based on the total number of carbon atoms presentin the mineral oil, and

(c) from about 10 to about 47 parts, by weight, of coupling agent, saidcoupling agent being characterized by

(i) being miscible in all proportions with said mineral oil,

(ii) having a total solubility parameter from about 8.2 to about 9.4,

(iii) having a polar and hydrogen bonding solubility parameter fromabout 3.2 to about 4.3,

(iv) having a non-polar solubility parameter from about 7.6 to about8.4,

(v) having a hydrogen bonding index number from about 6.0 to about 12.0,and

(vi) being substantialy non-reactive with said polyisocyanate prepolymerand said polyol.

The prepolymer is formed by the reaction of a polyisocyanate compoundwith a polyol as defined above. In addition, at least about 0.25equivalents of the polyisocyanate compound per 1.0 equivalents of thepolyisocyanate compound used is a liquid long chain aliphaticpolyisocyanate. The resulting mineral oil extended polyurethane is alsocharacterized by the presence of a polydiene moiety in the polyurethanestructure.

In another aspect, the present invention relates to a process forreclaiming or sealing an insulated electrical device by introducing intosaid device, a composition which cures into a grease compatible, cured,cross-linked, mineral oil extended polyurethane which is non-spewing andwhich is comprised of a defined polyurethane and/or a defined mineraloil and/or a defined coupling agent, wherein at least two of the definedmaterials are present in each instance.

In a further aspect, the present invention relates to an insulatedelectrical device containing the grease compatible, cured, cross-linked,mineral oil extended polyurethane which is non-spewing and which iscomprised of a defined polyurethane and/or a defined mineral oil and/ora defined coupling agent, wherein at least two of the defined materialsare present in each instance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view, partly in section, of a length of aplastic insulated, multi-conductor telephone cable.

DESCRIPTION OF PREFERRED EMBODIMENTS

As stated hereinabove, one aspect of the present invention relates to agrease compatible, cured, cross-linked, mineral oil extendedpolyurethane which is non-spewing. Although the mineral oil extendedpolyurethane of the present invention may be used in a variety ofdifferent products, such as a waterproofing membrane in the constructionfield, a liquid casting system for potting or as a solid lubricant toreplace grease in certain situations, in the interest of brevity andclarity, it will be described in the present specification in connectionwith the reclamation or sealing (encapsulation) of electrical devices,and particularly the sealing of insulated electrical devices containinggrease.

In the present specification, the term "grease compatible" is used toindicate the substantial reduction or elimination of the tendency of themineral oil to migrate toward the interface of the grease and themineral oil extended polyurethane. The migration phenomenon is evidencedby a film or pool of separated mineral oil at the interface and in thisregard, should be distinguished from exudation or spewing whereinmineral oil separates from the polyurethane throughout the mineraloil-polyurethane system and irrespective of the presence of grease.

The grease may be any of those which are typically employed ininsulated, multi-conductor electrical devices, such as undergroundtelephone cables. One type of grease which is commonly used in insulatedelectrical devices is a highly paraffinic mineral which contains fromabout 10 to about 15%, by weight, of a low molecular weight polyolefinsuch as polyethylene. To form the grease, the polyolefin is melted,combined with the mineral oil and allowed to solidify. Another type ofgrease is a petroleum jelly which generally has a specific gravity offrom about 0.815 to about 0.880 (at 60° C.) and a melting point in therange of from about 38° to about 60° C. The grease is typically preparedby the fractional distillation of still residues, from the steamdistillation of paraffin-base petroleum or from steam-reduced crude oilsfrom which the light fractions have been removed. Since the grease isprimarily composed of aliphatic constituents, it is believed that themigration phenomenon is caused by the preferential attraction of thegrease for the mineral oil. It is to be understood, however, thatapplicants do not wish to be bound by this theory.

To eliminate or substantially reduce the above-described migrationphenomenon, it has been found that it is necessary to particularlydefine the polyurethane and/or the mineral oil and/or the coupling agentused in the preparation of the grease compatible, cured, cross-linked,mineral oil extended polyurethane. While some reduction of migration isobtained by particularly defining one of the components, a significantreduction in migration is obtained by particularly defining two of thecomponents and essentially all of the migration is eliminated byparticularly defining the polyurethane, the mineral oil, and thecoupling agent.

The grease compatible, cured, cross-linked, mineral oil extendedpolyurethane is generally comprised of from about 8 to about 45 parts ofpolyurethane, from about 20 to about 75 parts of mineral oil and fromabout 10 to about 47 parts of coupling agent, all parts expressed on aweight basis.

For lower mineral oil extended polyurethanes which are particularlyuseful for a variety of potting and encapsulating applications (e.g.,splicing), the grease compatible, cured, cross-linked, mineral oilextended polyurethane is comprised of from about 25 to about 45 parts ofpolyurethane, from about 20 to about 40 parts of mineral oil and fromabout 25 to about 47 parts of coupling agent, all parts expressed on aweight basis.

Preferably, the grease compatible, cured, cross-linked mineral oilextended polyurethane is comprised of from about 30 to about 35 parts ofpolyurethane, from about 24 to about 38 parts of mineral oil and fromabout 30 to about 41 parts of coupling agent, all parts expressed on aweight basis.

The polyurethane which is used in the grease compatible, cured,cross-linked, mineral oil extended polyurethane of the present inventionis generally prepared by reacting a polyisocyanate with a polyol. In afirst embodiment, the polyisocyanate is a polyisocyanate compound whichdirectly reacts with the polyol in the presence of the mineral oil andthe coupling agent to form the mineral oil extended polyurethane. In asecond and more preferred embodiment, the polyisocyanate is apolyisocyanate prepolymer which is in turn prepared by reacting anexcess of a polyisocyanate compound with a polyol in a manner well knownin the art. The polyisocyanate prepolymer is then reacted with thepolyol in the presence of the mineral oil and the coupling agent to formthe mineral oil extended polyurethane. The manner in which thepolyisocyanate is reacted with the polyol will be discussed in detailbelow.

The polyisocyanate compound which is reacted with the polyol to form thepolyurethane or which is used in the preparation of the polyisocyanateprepolymer may be an aliphatic polyisocyanate, a cycloaliphaticpolyisocyanate or an aromatic polyisocyanate. Typical of suchpolyisocyanate compounds are 3-isocyanatomethyl3,5,5-trimethylcyclohexyl isocyanate (IPDI), toluene diisocyanate (TDI),4,4'-diphenylmethane diisocyanate (MDI), polymethylenepolyphenylisocyanate, 1,5-naphthalene diisocyanate, phenylenediisocyanates, 4,4'-methylene bis (cyclohexyl isocyanate) (H₁₂ MDI),hexamethylene diisocyanate (HMDI), biuret of hexamethylene diisocyanate,2,2,4 trimethylhexamethylene diisocyanate and combinations thereof, aswell as related aromatic, aliphatic and cycloaliphatic polyisocyanateswhich may be substituted with other organic or inorganic groups that donot adversely affect the course of the chain-extending and/orcross-linking reaction.

While any of the polyisocyanates described above may be used in thepreparation of the mineral oil extended polyurethane of the presentinvention, it has been found that to aid in the reduction of themigration of the mineral oil, at least about 0.25 equivalents per 1.0equivalents of the polyisocyanate compound used, should be a liquid longchain aliphatic polyisocyanate having from about 12 to about 100,preferably from about 12 to about 50 carbon atoms in the carbon chain.The term "aliphatic", as used herein, includes those carbon chains whichare substantially non-aromatic in nature. They may be saturated orunsaturated, unbranched, branched or cyclic in configuration and maycontain substituents which do not adversely affect migration. Exemplaryof the liquid long chain aliphatic polyisocyanates are dodecyldiisocyanate, tridecyl diisocyanate, etc. An especially preferred longchain polyisocyanate is a mixture of polyisocyanate isomers derived froma 36 carbon dimer aliphatic acid (hereafter DDI). This mixture ofpolyisocyanate isomers is available from General Mills Chemicals, Inc.,under the trademark DDI DIISOCYANATE.

It is to be understood that the term "long chain aliphaticpolyisocyanate" is also intended to encompass combinations of suitablepolyisocyanates. In other words, to reduce migration, at least about0.25 equivalents of polyisocyanate compound per 1.0 equivalents of thepolyisocyanate compound used in the preparation of the prepolymer ofwhich is directly reacted with a polyol to form the polyurethane, mustbe one or a combination of the liquid long chain aliphaticpolyisocyanates.

From a reduction in migration standpoint, it is preferable to employ apolyisocyanate which is entirely composed of DDI. However, at present,it is economically preferable to mix the DDI with other polyisocyanatessuch as MDI and polymethylene polyphenylisocyanate (available fromUpjohn Company under the trademark PAPI). Particularly acceptableresults are obtained from a polyisocyanate mixture comprised of about0.25 equivalents of DDI and about 0.75 equivalents of PAPI per 1.0equivalents of polyisocyanate compound used in the preparation of thepolyurethane.

The polyol which is reacted with the polyisocyanate compound and thepolyol which is reacted with the prepolymer is selected from the groupconsisting of castor oil, polyether polyols, hydroxyl bearinghomopolymers of dienes, hydroxyl bearing copolymers of dienes, andcombinations thereof. Although not critical to the formation of thepolyurethane, the polyols generally have a number average molecularweight between about 1,000 and about 6,000, preferably between about1,000 and about 4,000.

The castor oil which may be used in the preparation of the mineral oilextended polyurethane is primarily composed of ricinolein which is aglyceride of ricinoleic acid. A typical castor oil comprises a mixtureof about 70% pure glyceryl triricinoleate and about 30% glyceryldiricinoleate-monooleate or monolinoleate and is available from NLIndustries, Inc., of Heightstown, N.J., as DB Oil.

Suitable polyether polyols include aliphatic alkylene glycol polymershaving an alkylene unit composed of at least 3 carbon atoms. Thesealiphatic alkylene glycol polymers are exemplified by polyoxypropyleneglycol and polytetramethylene ether glycol. Also, trifunctionalcompounds exemplified by the reaction product of trimethylol propane andpropylene oxide may be employed.

The hydroxyl bearing homopolymers of dienes or hydroxyl bearingcopolymers of dienes are prepared from dienes which includeunsubstituted, 2-substituted or 2,3-disubstituted 1,3-dienes of up toabout 12 carbon atoms. Preferably, the diene has up to about 6 carbonatoms and the substituents in the 2- and/or 3-position may be hydrogen,alkyl, generally lower alkyl, e.g., of about 1 to about 4 carbon atoms,substituted aryl, unsubstituted aryl, halogen, etc. Typical of suchdienes are 1,3-butadiene, isoprene, chloroprene, 2-cyano-1,3-butadiene,2,3-dimethyl-1,3,butadiene, etc. The preferred dienes are 1,3-butadieneand isoprene.

In the preparation of hydroxyl bearing copolymers of dienes,olefinically unsaturated monomers are generally employed in conjunctionwith the previously discussed dienes. The acceptable monomers includealpha-mono-olefinic materials of from about 2 to about 12 carbon atoms,such as styrene, vinyl toluene, methyl methacrylate, acrylonitrile, etc.Styrene is especially preferably as the copolymerizable monomer.

A description of the dienes, copolymerizable monomers and the hydroxylbearing homopolymers and copolymers prepared therefrom which may beemployed in the present invention is set forth in U.S. Pat. No.3,714,110, the content of which is incorporated by reference.

The preferred hydroxyl bearing homopolymer of butadiene is generally inliquid form and has the approximate structure: ##STR1## wherein n=57-65.

The preferred hydroxyl bearing copolymer of butadiene and styrene hasthe approximate structure: ##STR2## wherein X is C₆ H₅ a =0.75

b=0.25

n=57-65

The hydroxyl bearing copolymer of butadiene and styrene generally hasthe following properties:

Butadiene, Wt.%=75

Styrene, Wt.%=25

Viscosity, poise at 30° C.=225

OH content meg./gm=0.65

Moisture, Wt.%=0.05

Iodine Number=335

The previously described hydroxyl bearing homopolymers of butadiene andhydroxyl bearing copolymers of butadiene are available from ArcoChemical Company under the trademark POLY-BD.

To enhance the compatibility of the mineral oil with the polyurethaneand thus aid in the prevention of spewing and migration, it has beenfound that the polyurethane structure must contain a polydiene moietywhich may be derived from hydroxyl bearing homopolymers of dienes,hydroxyl bearing copolymers of dienes or combinations thereof. Theproportion of the polydiene moiety required in the polyurethanestructure to reduce spewing and migration is dependent upon a number ofvariables such as the polyisocyanate compound, the type and amount ofmineral oil and the type and amount of coupling agent. For a givensystem, the amount of polydiene moiety in the polyurethane structure istypically determined by routine experimentation well within the scope ofexpertise of one of ordinary skill in the art. In general, it ispreferable that at least about 0.25 equivalents per 1.0 equivalents ofthe total polyol used in the preparation of the polyurethane be selectedfrom the group consisting of hydroxyl bearing homopolymers of dienes,hydroxyl bearing copolymers of dienes, and combinations thereof.

In the embodiment of the present invention wherein a polyisocyanateprepolymer is used, either a portion or all of the polyol which is usedin the preparation of the polyisocyanate prepolymer and/or either aportion or all of the polyol which is reacted with the prepolymer is ahydroxyl bearing homopolymer of a diene, a hydroxyl bearing copolymer ofa diene or a combination thereof. In other words, the source of thepolydiene moiety is not of importance as long as there is an adequatetotal amount of a hydroxyl bearing homopolymer of a diene, a hydroxylbearing copolymer of a diene or combination thereof, used in thepreparation of the polyurethane.

The functionality of the polyisocyanate and the polyol are each in therange of from 2.0 to about 3.0, preferably from about 2.2 to about 2.7.In order to provide suitable mechanical and electrical properties forthe reclamation or sealing of insulated electrical devices within areasonable period of time at ambient temperature, the mineral oilextended polyurethane should be cross-linked. Cross-linking may beobtained by using a polyisocyanate, a polyol, or both having afunctionality greater than 2.0.

The hydroxyl functionality and molecular weight of several of thepolyols which are suitable for use in the present invention are setforth in Table A.

                  TABLE A                                                         ______________________________________                                                          OH                                                            Polyol          Functionality                                                                             M.W.                                            ______________________________________                                        Polybutadiene     2.3-2.4     2912-3038                                       Styrene-Butadiene Copolymer                                                                     2.0         3280                                            Castor Oil        2.7         923                                             Polyoxypropylene Glycol                                                                         2.0         2040                                            Trimethylol Propane/Propylene                                                 Oxide Reaction Product                                                                          3.0         4145                                            Polytetramethylene Ether Glycol                                                                 2.0         2004                                            ______________________________________                                    

The ratio of the number of isocyanate groups to the number of hydroxylgroups in the polyurethane reactants is preferably between about 1.0 andabout 1.3 to provide the desired polymer structure, even in the presenceof minor amounts of water.

The mineral oils which may be used in the preparation of the mineral oilextended polyurethanes of the present invention include those aliphatic,cycloaliphatic and branched aliphatic saturated hydrocarbons whichcontain from about 15 to about 30 carbon atoms and which are distilledfrom petroleum. It is to be understood that the terms "mineral oil" and"aliphatic, cycloaliphatic and branched aliphatic saturatedhydrocarbons", as used herein, are given their common industrial meaningso that the mineral oil may contain minor amounts of aromatic oils.

The mineral oils described above eliminate or substantially reduce theplastic connector and sheathing deterioration and health problems of theprior art wherein substantially pure aromatic oil was generally used.However, to reduce the tendency of the mineral oil to migrate to thegrease interface, it has now been found that it is preferable to havethe mineral oil include some aromatic oil. In general, the amount ofaromatic carbon atoms in the mineral oil should be sufficient to reducethe migration phenomenon but should not cause the level of deteriorationand health problems associated with the aromatic oil systems of theprior art. Thus, the mineral oil generally has from about 1.0 to about30% aromatic carbon atoms, typically from about 5.0 to about 25%aromatic carbon atoms, and preferably from about 14 to about 25%aromatic carbon atoms, based on the total number of carbon atoms presentin the mineral oil. The most preferred mineral oil contains about 20%aromatic carbon atoms.

In order to effectively compatibilize the mineral oil with thepolyurethane, i.e., to prevent spewing, a coupling agent must be used informing the mineral oil extended polyurethane of the present invention.The coupling agent must satisfy several criteria. First, it must bemiscible in the mineral oils in all proportions. In other words, thecoupler should be miscible in all proportions with mineral oils to forma true solution (i.e., one part coupler/99 parts mineral oil or 99 partscoupler/one part mineral oil).

Next, the coupling agent must have a total solubility parameter (δ_(T))in the range of from about 7.0 to about 9.5, preferably from about 7.2to about 9.5. The (δ_(T)) value of a substance is calculated accordingto the formula

    δ.sub.T =(ΔE/V).sup.1/2

where E is the energy of vaporization to a gas at zero pressure (i.e.,an infinite separation of the molecules); and V is the molar volume ofcomponent present. The dimensions of δ_(T) are (calories per cubiccentimeter)^(1/2). Since it is possible to ascertain E and V for mostsubstances, the value of the total solubility parameter or δ_(T) may becalculated from the heat of vaporization ΔH, since it can be shown that

    ΔE25° C.=ΔH25° C.-592

Since the value of ΔH at 25° C. for most compounds may be found in theliterature, this value may be used to calculate ΔE and then δ_(T).Further details on total solubility parameters and means for theircalculation are found in an article entitled Solubility Parameter Valuesby H. Burrell and B. Immergut at P.IV-341, of Polymer Handbook edited byJ. Brandrup and E. H. Immergut, 3rd Edition Interscience Publ. June1967.

It has also been determined that the coupling agent of this inventionhas a hydrogen bonding index number in the range of from about 6.0 toabout 12.0, preferably from about 8.2 to about 8.8. The hydrogen bondingindex number (γ) of a compound is a measurement of its proton (hydrogen)attracting power. The hydrogen bonding index number (γ) (protonattracting power) of a compound is measured by comparing the relativestrengths of the hydrogen bonds which the liquid compounds forms with acommon proton or Deuterium donor.

In practice, this is done by dissolving deuterated methanol in theliquid to be tested. The proton attracting power of a liquid compound isdetermined by measurement of the movement produced on the OD vibrationalband of CH₃ OD. The OD vibrational band occurs at 4μ in the liquid CH₃OD and at 3.73μ in the monomolecular CH₃ OD in dilute benzene solution.Benzene is considered to have an OD vibrational shift of 0. Theformation of hydrogen bonds shifts the monomolecular band to lowerfrequencies or longer wave lengths. The stronger the proton attractingpower of a liquid, the greater is the shift which it produces on the ODband. By Infrared Spectroscopy the perturbations of the OD band can beestablished.

The γ value of a compound may be determined by measuring the shift inwave numbers of the OD vibrational band after dissolution in the liquidcompound and dividing the resulting number by 10. (Wave number is thereciprocal of an angstrom unit). Those compounds having a γ number of 0to about 6.0 are generally acknowledged to be weak hydrogen bondacceptors. Compounds having index numbers in the range of from about 6.0to about 12.0 are usually considered moderate hydrogen bond formers andthose having index numbers above about 12.0 are considered to be stronghydrogen bonders. The coupling agents useful in this invention are thosehaving a hydrogen bonding index number (γ) falling in the range betweenabout 6.0 and about 12.0 as determined by the above-mentioned technique.The origin of the Hydrogen Bonding index system and additional detailson the means for its computation are found in a series of articles by W.J. Gordy in J. Chem. Physics, Vol. VII, pp. 93-99, 1939, Vol. VIII, pp.170-177, 1940 and Vol. IX, pp. 204-214, 1941.

In the screening of potential coupling agents, the determination of thetotal solubility parameter and the hydrogen bonding index number can bemade using well-known analytical techniques as described above. Thetotal solubility parameter and hydrogen bonding index number for manycompounds are also available in the literature and may be determined byreference to the appropriate text.

The coupling agent is further selected so that it is non-reactive orsubstantially non-reactive with respect to the polyurethane-formingreactants or precursor (polyol, polyisocyanate, polyisocyanateprepolymer). That is, the coupling agent should not interfere with theformation of the polyurethane. Coupling agents which satisfy thiscriterion generally do not contain any labile hydrogen atoms in theirstructure.

In order to prevent evaporation, the coupling agent should have aboiling temperature above about 220° F. It is to be understood that thisboiling temperature is solely a practical consideration and is notcritical to the efficacy of the coupling agent in preventing spewing.Thus, in those environments wherein the temperature remains relativelylow, a coupling agent having a boiling temperature significantly below220° F. may be utilized.

Chemical compounds which satisfy the above criteria are generally liquidesters, ketones, and those compounds in which a polar group is attachedto an alkyl structure, such as trialkyl phosphate. The coupling agentmay contain one or more characteristic functional groups. That is, forexample, the coupling agent may be a mono-, di-, or tri-ester as long asit meets the above criteria. The coupling agent may also be saturated orunsaturated and may be aromatic-aliphatic, cycloaliphatic or whollyaliphatic. A partial list of the coupling agents which may be used toprevent spewing is set forth in Table B:

                  TABLE B                                                         ______________________________________                                        Coupling Agents                                                                                   Solubility Parameters                                                         (in Cal/per CC).sup.1/2                                   Chemical Name         δT                                                                             δPH                                                                             δNP                                ______________________________________                                        1.   2,2,4 Trimethyl-1,3                                                           Pentanediol Diisobutyrate                                                                          8.2    4.3   6.9                                    2.   Di-2-ethylhexyl Sebacate                                                                           8.6    *     *                                      3.   Acetyl Tributyl Citrate                                                                            9.2    *     *                                      4.   Di-2-ethylhexyl Adipate                                                                            8.5    3.8   7.6                                    5.   Diisodecyl Phthalate 8.8    4.0   7.8                                    6.   Dioctyl Adipate      8.5    3.8   7.6                                    7.   Tributyl Phosphate   8.6    *     *                                      8.   Dibutyl Fumarate     9.0    5.7   6.9                                    9.   Acetyl Di-2-ethylhexyl Citrate                                                                     8.6    *     *                                      10.  Di-n-butyl Sebacate  8.8    *     *                                      11.  Dioctyl Phthalate    9.0    4.4   7.9                                    12.  Di-2-ethylhexyl Citrate                                                                            8.6    *     *                                      13.  Isobutyl Acetate     8.4    4.6   7.1                                    14.  Methyl ethyl Ketone  9.4    6.4   6.9                                    15.  Methyl-n Butyl Ketone                                                                              8.6    5.2   6.9                                    16.  Diundecyl Phthalate  8.8    3.8   7.9                                    17.  2-ethylhexyl Trimellitate                                                                          9.0    4.3   7.9                                    18.  Ditridecyl Adipate   8.5    3.2   7.9                                    ______________________________________                                         *Indicates values not calculated.                                        

The coupling agents described above are effective in reducing orsubstantially eliminating spewing in the previously defined mineral oilextended polyurethanes. To reduce migration, however, it has been foundthat the coupling agent must be even more precisely defined.Specifically, a reduction in migration is obtained by employing acoupling agent having the above-enumerated miscibility with mineral oil,hydrogen bonding index number range, non-reactiveness and, preferably,boiling temperature, but having a total solubility parameter in thenarrower range of from about 8.2 to about 9.4, preferably from about 8.7to about 9.2, and most preferably from about 8.8 to about 9.0. The totalsolubility parameter (δ_(T)) is composed of three components, namely thepolar solubility parameter (δ_(P)), the hydrogen bonding solubilityparameter (δ_(H)) and the non-polar solubility parameter (δ_(NP)). Thethree components are related to the total solubility parameter accordingto the equation: ##EQU1##

The separation of δ_(T) into the individual components is accomplishedby initially calculating the aggregation number (α) from the equation##EQU2## wherein T_(b) is the boiling temperature in degrees absolute,T_(c) is the critical temperature in degrees absolute, M is themolecular weight and ρ is the density of the material.

From α and δ_(T) the hydrogen bonding solubility parameter may becalculated from the equation: ##EQU3##

The polar solubility parameter is determined from the equation: ##EQU4##wherein ΣF_(P) is the sum of all the polar molar cohesion constants andΣF_(T) is the sum of all the molar cohesion constants.

From δ_(T), δ_(P) and δ_(H), the non-polar solubility parameter (δ_(NP))may be calculated from the equation: ##EQU5##

Additional details of the various solubility parameters may be found ina book by K. L. Hoy entitled Tables of Solubility Parameters, publishedby Union Carbide Corp., July 21, 1969, and an article by K. L . Hoy inJ. of Paint Tech., Vol. 42, No. 541, pp. 76-118, February, 1970.

To simplify the use of δ_(P) δ_(H) and δ_(NP) in determining couplingagents which are useful in reducing migration, δ_(P) and _(H) have beencombined to yield a polar and hydrogen bonding solubility parameter(δ_(PH)) according to the equation: ##EQU6##

To aid in the reduction of migration, it has been found that thecoupling agent must possess a total solubility parameter within theranges discussed above, but must additionally possess a polar andhydrogen bonding solubility parameter (δ_(PH)) in the range of fromabout 3.2 to about 4.3, preferably from about 3.8 to about 4.2, and anon-polar solubility parameter in the range of from about 7.6 to about8.4, preferably from about 7.8 to about 8.2. The polar and hydrogenbonding parameter and the non-polar solubility parameter for somecoupling agents are included in Table B.

Thus, of those coupling agents set forth in Table B, di-2-ethylhexyladipate, dioctyl adipate, diundecyl phthalate, 2-ethylhexyl trimellitateand ditridecyl adipate may be used in reducing migration. Diundecylphthalate, 2-ethylhexyl trimellitate and ditridecyl adipate areespecially preferred as the coupling agent.

Selection of a particular coupling agent and determination of thecorrect amount to be employed is determined by simple experimentationand will vary from one mineral oil extended polyurethane to another. Theselection is dependent upon chemical and physical differences in variouspolyisocyanate compounds and polyols as well as upon the desired amountof mineral oil extension in the cured, cross-linked mineral oil extendedpolyurethane. Thus, for example, a greater amount of a less preferredcoupling agent will generally be required to obtain the same degree ofgrease and mineral oil compatibility when compared to a more preferredcoupling agent. While the above-description has been made with referenceto a single coupling agent, it is to be understood that combinations ofcoupling agents may also be used in reducing or eliminating spewingand/or migration and are therefore to be considered within thedefinition of "coupling agent."

The grease compatible, mineral oil extended polyurethane of the presentinvention may be used in the reclamation or sealing (encapsulation) ofair core cables, but it is particularly useful in the reclamation orsealing of grease-containing electrical devices such as multi-pairtelephone cables.

In a typical cable such as that illustrated in FIG. 1, a plurality ofwire conductors 1 are disposed within the central core 2 of the cable.Each wire is surrounded by an insulating material, generally apolyolefin or polyester plastic. For a grease-containing cable, greaseis generally found in the free spaces between the insulated wires. Theplurality of insulated wires are tightly enclosed within a spiral woundsheath 3, usually a polyethylene terephthalate sheet material.Surrounding the sheath are two protective shields 4, made of a flexiblemetal sheeting such as aluminum. he shields are separated from oneanother by a continuous layer 5 of a suitable insulating material.Finally, an outer jacket 6 of a protective plastic such as polyethylene,covers the outermost aluminum layer and serves to protect the cable.

Aqueous contaminants generally find their way into the cable throughpinholes and stress cracks that develop around fittings and cableconnectors, ultimately lodging in the interior free spaces of thecentral core 2 of the cable. After a particular aqueous contaminant, forexample water, has been present for some time in the core, theelectrical properties of the cable can be deleteriously effected. Atthis point, the present invention may be employed to restore the cableto substantially its original operating condition.

The reclaiming operation of the present invention is generally carriedout on location. As stated above, the polyurethane may be prepared byeither reacting a polyisocyanate compound with a polyol or apolyisocyanate prepolymer with a polyol. In the first embodiment, thedesired amounts of polyisocyanate compound, polyol, mineral oil andcoupling agent are initially mixed together to form a single phasesystem. Catalyst and other known additives such as moisture scavengers(e.g., benzoul chloride), antioxidants, fungicides, pigments, etc.,which are commonly used in the art and which do not adversely affect thepolyurethane reaction may also be incorporated into the mixture. Theamount and type of catalyst and other additives, as is known by thoseskilled in the art, is dependent, for example, on the precursorcomposition, the utility intended, the cure time desired, and ambientconditions present.

The composition comprised of the polyurethane precursor (i.e., thepolyisocyanate compound and the polyol or the polyisocyanate prepolymerand the polyol), the mineral oil, the coupling agent, and, optionally,the catalyst and other additives, has an initial viscosity, at fromabout 15° C. to about 50° C., within the range of from about 10 to about100 centipoise. It is important that the viscosity of the composition bekept relatively low in order to effect its introduction into the freespaces of a cable that is to be reclaimed. However, the amount ofpolyurethane precursor in the composition should also be kept low inorder to prevent excessive weight gain in the electrical device to bereclaimed or sealed as well as for reasons of economy.

To introduce the composition into the cable, a small portion of thecable outer protective layers including jacket 6, aluminum protectiveshields 4 and sheath 3 are removed and a nipple (not shown) installed inthe opening thus formed, using techniques that are well-known in thetrade. This operation can be carried out from above, or below, andwithout removing the cable from its resting place. The compositionhaving just been formed has a relatively low viscosity and is easilyintroduced into the core of the cable through a hose (not shown)connected to the nipple. Continuous pumping of the low viscositycomposition is maintained in order to drive it along the length of thecable. After the composition has been injected into the cable, thedelivery hose is withdrawn from the nipple and the hole in the nipple issealed with a plug (not shown). The introduction operation will havedriven the composition through the interior-free spaces of the cable andwill displace the fluid penetrants and some of the grease (in a greasecontaining cable) in the interior free spaces (e.g., between theindividual wires and the outer polyethylene terephthalate sheath).

Conveniently within from about 1.0 to about 120 hours after injectioninto an insulated electrical device, the composition cures to form agrease compatible, cured, cross-linked, mineral oil extendedpolyurethane which is non-spewing and which has a viscosity on the orderof about 1000 centipoise. The mineral oil extended polyurethane isphysically and chemically stable and does not lose mineral oil byexudation, spewing or migration. The hydrophobic nature of the cured,mineral oil extended polyurethane also serves to seal the cable againstsubsequent penetration of water or other fluid materials. Furthermore,the cured, mineral oil extended polyurethane has good insulatingproperties due to its relatively low dielectric constant and high volumeresistivity.

When employing the grease compatible, mineral oil extended polyurethaneas an encapsulant, a higher proportion of polyurethane is generallyused, as stated above. The cable which is to be repaired or spliced isexposed and the insulating material 5, protective shields 4 and spiralwound sheath 3, is removed. After the repair or splice has beencompleted, a mold, typically composed of a plastic material, whichconforms to the circumference of the cable is attached. The mold has aport through which is poured the composition comprising the polyurethaneprecursor, mineral oil, coupling agent and, optionally, catalyst andother conventional additives (as discussed above). Although theviscosity of the sealing composition is generally greater than that usedin reclamation, the relatively low viscosity sealing composition isgenerally maintained in the vicinity of the repair or splice by placingclamps around the cable at both ends of the mold. In from about tenminutes to about four hours (depending on the catalyst, ambientconditions, etc.), the polyurethane precursor has desirably reacted toform a non-spewing, grease compatible, cured, cross-linked, mineral oilextended polyurethane which has a viscosity of about 100,000centipoises. The clamps are then generally removed and the cable isreburied. The mold is usually left in place to provide additionalstructural support and protection for the cable. The non-spewing, greasecompatible, cured, cross-linked, mineral oil extended polyurethaneencapsulant provides a hydrophobic barrier against water or fluidpenetration.

In the embodiment wherein a polyisocyanate prepolymer is employed, thecontents of two separate containers are preferably mixed inapproximately equal amounts to form the composition which is to beintroduced into the insulated electrical device, such as an undergroundtelephone cable. In this manner, instruction of installing personnel inthe formulation and use of the composition is greatly facilitated.

In one container is the polyisocyanate prepolymer, which may bedissolved in mineral oil or, preferably, in a coupling agent. Whenreclamation is to be undertaken, between about 50 and about 200, andpreferably about 100 grams of the polyisocyanate prepolymer is used perliter of solution. When encapsulation is to be performed, between about200 and about 600, preferably about 400 grams of the polyisocyanateprepolymer is used per liter of solution.

In the second container is preferably a solution of between about 75 andabout 200 and preferably about 150 grams per liter of polyol in mineraloil when reclamation is contemplated. When encapsulation is to beperformed, between about 250 and about 500, preferably about 400 gramsof polyol is used per liter of solution. In those instances where acatalyst is used, it is typically included in the contents of the secondcontainer.

The coupling agent may be added to the contents of the first container,the second container, or, preferably, both containers. The importantconsideration is that there be sufficient coupling agent in the overallcomposition to obtain a single phase system comprising the polyurethaneprecursor (i.e., the polyisocyanate prepolymer and the polyol), themineral oil and the coupling agent. It is only by the use of this singlephase system that a non-spewing, grease compatible, cured, cross-linked,mineral oil extended polyurethane may be obtained. The known additivesmay also be added to either or both of the containers.

After the contents of the two containers are mixed to form a lowviscosity composition, the composition is then employed to reclaim orseal insulated electrical devices, such as underground cables, in themanner discussed above. A noted advantage of using the polyisocyanateprepolymer embodiment is that the composition generally requires lesstime to cure and form the non-spewing, grease compatible, cured,cross-linked, mineral oil extended polyurethane.

Whether the polyisocyanate compound embodiment or the polyisocyanateprepolymer embodiment is employed, the low viscosity composition ischaracterized by a low volatility (vapor pressure) and an inoffensiveodor. Since the aromatic content of even the most preferred mineral oilis maintained relatively low, the toxicity of the composition issubstantially less than the toxic products previously employed inreclamation techniques. When cured, the mineral oil extendedpolyurethanes do not spew even at higher extensions, colder temperaturesor over extended periods of time. Furthermore, the tendency of themineral oil to migrate to the grease interface is eliminated orsubstantially reduced. The mineral oil extended polyurethanes of thepresent invention also do not chemically attack the polycarbonateconnectors and polyolefin, polyethylene terephthalate or other polymermaterials which are typically used in cable manufacture.

The non-spewing, grease-compatible, cured, cross-linked, mineral oilextended polyurethane formed in either the reclaiming or sealing(encapsulating) of electrical devices, generally possesses a gel-likeconsistency. The term "gel-like" is used in the present specification todescribe a relatively soft, non-brittle substance which isdistinguishable from those extended polyurethanes having the consistencyof hard plastic, wood or concrete. Although the actual consistency ofthe mineral oil extended polyurethane of the present invention may varyfrom a gellatin (evident in reclaimed devices) to a soft, sponge rubber(evident in encapsulated devices), the term "gel-like" is used toencompass such variations.

The electrical properties of the grease compatible, cured, cross-linked,mineral oil extended polyurethanes are excellent. Specifically, themineral oil extended polyurethanes generally possess a relatively lowdielectric constant of less than about 4.0 at 1 KhZ (as determined byASTM D-150) and a volume resistivity of at least about 2.5×10¹⁰ ohm-cm(as determined by ASTM D-257).

A further understanding of the present invention may be obtained withreference to the following examples. It is to be understood, however,that the invention is not limited to the embodiments described in theexamples.

In Examples I-IV, the cured, cross-linked, mineral oil extendedpolyurethane is prepared from a polyisocyanate prepolymer and a polyolin a manner similar to that described in Example V. The cured,cross-linked, mineral oil extended polyurethane is then placed incontact with the grease. In Examples V and VI, the mineral oil extendedpolyurethane was allowed to cure while in contact with the grease.

EXAMPLE I

This example illustrates the effects on migration of aromatic, aliphaticand cycloaliphatic polyisocyanate compounds.

The mineral oil extended polyurethane is comprised of:

35% Polyurethane

30% Dioctyl Adipate

35% Mineral Oil (Drakeol 35*) All percentages being on a weight basis.The amount of polyurethane includes 0.17% antioxidant (a thio-bis-phenolavailable from Uniroyal Co., Inc. as AO 439), 0.015% catalyst (dibutyltin dilaurate) and 0.03% moisture scavenger (benzoyl chloride).

The polyurethane is prepared from 0.61 equivalents of a hydroxyl bearinghomopolymer of butadiene, 0.39 equivalents of castor oil and 1.08equivalents of polyisocyanate compound. The mineral oil weight loss,based on the total weight of the mineral oil extended polyurethane,after seven days of contact with grease may be seen in Table C.

                  TABLE C                                                         ______________________________________                                                                 Weight Loss                                            Polyisocyanate         (%)                                                  ______________________________________                                        4,4'-methylene bis (cyclohexyl isocyanate)                                                             1.5                                                  DDI                       0.35                                                Biuret of hexamethylene diisocyanate                                                                   2.9                                                  2,2,4 trimethyl-hexamethylene diisocyanate                                                             1.8                                                  Polymethylene polyphenylisocyanate                                                                     2.7                                                  ______________________________________                                    

EXAMPLE II

This example illustrates the effects of blending polymethylenepolyphenylisocyanate (PAPI) with DDI with respect to oil migration andreactivity (gel time). The mineral oil extended polyurethane iscomprised of:

35% Polyurethane

30% Diundecyl Phthalate

35% Mineral Oil (Circosol 4130*)

All percentages being on a weight basis. The amount of polyurethaneincludes 0.17% antioxidant (AO 439), 0.02% fungicide(2-(4-thiazolyl)benzimidazole), 0.01% benzoyl chloride and an amount ofcatalyst indicated in Table D.

The polyurethane is prepared from 0.61 equivalents of hydroxyl bearinghomopolymer of butadiene, 0.39 equivalents of castor oil and 1.08equivalents of a polyisocyanate compound. The effects of varying theproportion of DDI in the polyisocyanate compound with respect to theweight loss, based on the total weight of the mineral oil extendedpolyurethane, and amount of catalyst required is set forth in Table D.

                  TABLE D                                                         ______________________________________                                                               WEIGHT                                                                        LOSS AFTER                                                                    1 MONTH                                                                       CONTACT   % T-12                                               PAPI    DDI    WITH      NEEDED FOR 30                                SAMPLE  (eg.)   (eg.)  GREASE (%)                                                                              MIN. GEL TIME*                               ______________________________________                                        A       0.0     1.08   0.0       0.6                                          B       0.27    0.81    0.38     0.6                                          C       0.54    0.54   0.0       0.6                                          D       0.81    0.27   0.0        0.06                                        E       1.08    0.0    16.00      0.06                                        ______________________________________                                         *T-12 is the catalyst dibutyl tin dilaurate. The gel time is defined as       the time required to reach 100,000 centipoise at 77° F.           

EXAMPLE III

This example illustrates the effects of the aromatic carbon content ofan oil on oil migration. The oil extended polyurethane is comprised of:

35% Polyurethane

30% Dioctyl Adipate

35% Oil

All percentages being on a weight basis. The amount of polyurethaneincludes 0.17% antioxidant (AO 439), 0.05% dibutyl tin dilaurate and0.01% benzoyl chloride.

The polyurethane is prepared from 0.61 equivalents of hydroxyl bearinghomopolymer of butadiene, 0.39 equivalents of castor oil and 1.08equivalents of polymethylene polyphenylisocyanate. The mineral oil lossafter seven days of contact with grease, using oils having varyingpercentages of paraffinic carbon atoms (C_(p)), naphthenic carbon atoms(C_(n)) and aromatic carbon atoms (C_(a)), based on the total number ofcarbon atoms present, is set forth in Table E.

                  TABLE E                                                         ______________________________________                                        Carbon Atom Sample                                                            Distribution (%)                                                                          A      B      C    D    E    F    G                               ______________________________________                                        C.sub.a     37.6   28.2   18.8 14.1  9.4 4.7   0                              C.sub.n     32.8   34.6   36.4 37.3 38.2 39.1 40                              C.sub.p     27.6   37.2   44.8 48.6 52.4 56.2 60                              Weight Loss (%)                                                                           0.41   1.21   1.36 1.61 2.06 2.56 2.41                            ______________________________________                                    

EXAMPLE IV

This example illustrates the effect of various coupling agents on oilmigration.

The mineral oil extended polyurethane is comprised of:

35% Polyurethane

30% Coupling Agent

35% Mineral Oil (Circosol 4130)

All percentages being on a weight basis. The amount of polyurethaneincludes 0.17% antioxidant (AO 439), 0.02% fungicide (2-(4-thiazolylbenzimidazole)) and 0.03% dibutyl tin dilaurate.

The polyurethane is prepared from 0.61 equivalents of hydroxyl bearinghomopolymer of butadiene, 0.39 equivalents of castor oil and 1.08equivalents of polymethylene polyphenylisocyanate. Table F sets forththe oil weight loss, based on the total weight of the mineral oilextended polyurethane, after one week contact with grease.

                  TABLE F                                                         ______________________________________                                        Coupling Agent     Weight Loss (%)                                            ______________________________________                                        Dioctyl Adipate    0.5                                                        Diundecyl Phthalate                                                                              0.23                                                       2-Ethylhexyl Trimellitate                                                                        0.13                                                       n-Octyl, n-decyl Trimellitate                                                                    0.35                                                       ______________________________________                                    

The following Examples illustrate a preferred method of preparing thegrease compatible, cured, crosslinked, mineral oil extendedpolyurethanes of the present invention.

EXAMPLE V

(a) Prepolymer Formation

A reactor fitted with an agitator, thermometer, nitrogen inlet andreflux condenser is charged with 35.11 grams (0.1170 eq.) of DDI and8.01 grams of castor oil (0.0234 eq.). The mixture is heated to about70° C. for about 11/2 hrs. under continuous agitation. To the mixture isadded 56.85 grams of ditridecyl adipate and the resulting mixture isagitated for about 1/2 hr. 0.03 grams of benzoyl chloride is then addedand the mixture agitated for about 1/4 hr. The mixture is then allowedto cool to room temperature. The resulting prepolymer has a theoreticalfree isocyanate content of 3.91%, by weight.

(b) Polyol Solution Preparation

Into a reactor similar to that used in the preparation of theprepolymer, is charged 2.23 grams (0.0065 eq.) of castor oil and 0.03grams of fungicide (2-(4-thiazolyl)benzimidazole). The mixture is heatedto about 77° C., under continuous agitation, for a period of about 3/4hr. or until the fungicide is dissolved. The mixture is cooled to about50° C. and 29.6 grams (0.0236 eq.) of a hydroxyl bearing homopolymer ofbutadiene, 47.20 grams of 4130 oil, 0.23 grams of antioxidant (AO 439)and 20.21 grams of ditridecyl adipate is added. The mixture is stirredfor about 3/4 hr. and then cooled to about 38° C. 0.50 grams of dibutyltin dilaurate is then added and the resulting mixture agitated for about1/2 hr. The mixture is then allowed to cool to room temperature.

(c) Polymer Formation

26.0 grams of the prepolymer is mixed with 74.0 grams of the polyol andthe resulting composition is allowed to cure while in contact withgrease. After 1 week, the non-spewing, grease compatible, cured,cross-linked, mineral oil extended polyurethane has no mineral oilweight loss. This demonstrates the effect on oil migration of a mineraloil extended polyurethane prepared from DDI, a mineral oil containing20% aromatic carbon atoms, based on the total number of carbon atomspresent in the mineral oil and ditridecyl adipate.

EXAMPLE VI

Example V is repeated except that the polyisocyanate compound used inthe preparation of the prepolymer is composed of 0.029 eq. of DDI and0.088 eq. of polymethylene polyphenylisocyanate. After 1 week, thenon-spewing, grease compatible, mineral oil extended polyurethane has nomineral oil weight loss.

Although the invention has been described with preferred embodiments, itis to be understood that variations and modifications may be resorted toas will be apparent to those skilled in this art. Such variations andmodifications are to be considered within the scope of the followingclaims.

We claim:
 1. A process for sealing an insulated electrical devicecomprising the steps of introducing into said device a compositioncomprising mineral oil, polyurethane precursor and coupling agent,(a)said polyurethane precursor comprising the reaction product of(i) apolyisocyanate compound or a polyisocyanate prepolymer prepared by thereaction of a polyisocyanate compound with a polyol selected from thegroup consisting of castor oil, polyether polyols, hydroxyl bearinghomopolymers of dienes, hydroxyl bearing copolymers of dienes, andcombinations thereof, wherein at least about 0.25 equivalents of thepolyisocyanate compound per 1.0 equivalents of the polyisocyanatecompound used is a liquid long chain aliphatic polyisocyanate, and (ii)a polyol selected from the group consisting of castor oil, polyetherpolyols, hydroxyl bearing homopolymers of dienes, hydroxyl bearingcopolymers of dienes, and combinations thereof, (b) said mineral oilbeing characterized by having from about 1.0 to about 30% aromaticcarbon atoms, based on the total number of carbon atoms present in themineral oil, and (c) said coupling agent being characterized by(i) beingmiscible in all proportions with said mineral oil, (ii) having a totalsolubility parameter from about 7.0 to about 9.5, (iii) having ahydrogen bonding index number from about 6.0 to about 12.0, and (iv)being substantially non-reactive with said polyisocyanate prepolymer andsaid polyol,reacting said polyol with said polyisocyanate in thepresence of said mineral oil and said coupling agent to obtain a greasecompatible, cured, cross-linked, mineral oil extended polyurethane whichis non-spewing, and which is characterized by the presence of apolydiene moiety in the polyurethane structure, and which comprises fromabout 8 to about 45 parts of polyurethane, from about 20 to about 75parts of mineral oil and from about 10 to about 47 parts of couplingagent, all parts expressed on a weight basis.
 2. The process of claim 1wherein the hydroxyl bearing homopolymers of dienes of claim 1, (a) (i)and (a) (ii) are hydroxyl bearing homopolymers of butadiene and whereinthe hydroxyl bearing copolymers of dienes of claim 1, (a) (i) and (a)(ii) are hydroxyl bearing copolymers of butadiene.
 3. The process ofclaim 1 wherein said liquid long chain aliphatic polyisocyanate containsfrom about 12 to about 50 carbon atoms in the carbon chain.
 4. Theprocess of claim 1 wherein the polyisocyanate compound used in thepreparation of the polyurethane comprises about 0.25 equivalents of amixture of polyisocyanate isomers derived from a 36 carbon dimeraliphatic acid and about 0.75 equivalents of polymethylenepolyphenylisocyanate per 1.0 equivalents of polyisocyanate compoundused.
 5. The process of claim 1 wherein the grease compatible, cured,cross-linked, mineral oil extended polyurethane comprises from about 25to about 45 parts of polyurethane, from about 20 to about 40 parts ofmineral oil and from about 25 to about 47 parts of coupling agent, allparts expressed on a weight basis, wherein said coupling agent isfurther characterized by having a boiling temperature above about 220°F. and being selected from the group consisting of a ketone and anester, and wherein said mineral oil is characterized by having fromabout 5.0 to about 25% aromatic carbon atoms, based on the total numberof carbon atoms present in the mineral oil.
 6. The process of claim 1wherein the polyisocyanate compound used in the preparation of thepolyurethane is a mixture of polyisocyanate isomers derived from a 36carbon dimer aliphatic acid.
 7. A process for sealing an insulatedelectrical device comprising the steps of introducing into said device acomposition comprising mineral oil, polyurethane precursor and couplingagent,(a) said polyurethane precursor comprising the reaction productof(i) a polyisocyanate compound or a polyisocyanate prepolymer preparedby the reaction of a polyisocyanate compound with a polyol selected fromthe group consisting of castor oil, polyether polyols, hydroxyl bearinghomopolymers of dienes, hydroxyl bearing copolymers of dienes, andcombinations thereof, wherein at least 0.25 equivalents of thepolyisocyanate compound per 1.0 equivalents of the polyisocyantecompound used is a liquid long chain aliphatic polyisocyanate, and (ii)a polyol selected from the group consisting of castor oil, polyetherpolyols, hydroxyl bearing homopolymers of dienes, hydroxyl bearingcopolymers of dienes, and combinations thereof and (b) said couplingagent being characterized by(i) being miscible in all proportions withsaid mineral oil, (ii) having a total solubility parameter from about8.2 to about 9.4, (iii) having a polar and hydrogen bonding solubilityparameter from about 3.2 to about 4.3, (iv) having a non-polarsolubility parameter from about 7.6 to about 8.4, (v) having a hydrogenbonding index number from about 6.0 to about 12.0, and (vi) beingsubstantially non-reactive with said polyisocyanate prepolymer and saidpolyol,reacting said polyol with said polyisocyanate in the presence ofsaid mineral oil and said coupling agent to obtain a grease compatible,cured, cross-linked, mineral oil extended polyurethane which isnon-spewing, and which is characterized by the presence of a polydienemoiety in the polyurethane structure, and which comprises from about 8to about 45 parts of polyurethane, from about 20 to about 75 parts ofmineral oil, and from about 10 to about 47 parts of coupling agent, allparts expressed on a weight basis.
 8. The process of claim 7 whereinsaid liquid long chain aliphatic polyisocyanate contains from about 12to about 50 carbon atoms in the carbon chain.
 9. The process of claim 7wherein the grease compatible, cured cross-linked, mineral oil extendedpolyurethane comprises from about 25 to about 45 parts of polyurethane,from about 20 to about 40 parts of mineral oil and from about 25 toabout 47 parts of coupling agent, all parts expressed on a weight basis,wherein said coupling agent is further characterized by having a boilingtemperature above about 220° F. and being selected from the groupconsisting of a ketone and an ester, and wherein said mineral oil ischaracterized by having from about 5.0 to about 25% aromatic carbonatoms, based on the total number of carbon atoms present in the mineraloil.
 10. The process of claim 7 wherein the hydroxyl bearinghomopolymers of dienes of claim 7 (a) (i) and (a) (ii) are hydroxylbearing homopolymers of butadiene and wherein the hydroxyl bearingcopolymers of dienes of claim 7, (a) (i) and (a) (ii) are hydroxylbearing copolymers of butadiene.
 11. The process of claim 7 wherein thepolyisocyanate compound used in the preparation of the polyurethanecomprises about 0.25 equivalents of a mixture of polyisocyanate isomersderived from a 36 carbon dimer aliphatic acid and about 0.75 equivalentsof polymethylene polyphenylisocyanate per 1.0 equivalents ofpolyisocyanate compound used.
 12. The process of claim 7 wherein thepolyisocyanate compound used in the preparation of the polyurethane is amixture of polyisocyanate isomers derived from a 36 carbon dimeraliphatic acid.
 13. The process of claim 1 wherein the coupling agent ischaracterized by(i) being miscible in all proportions with said mineraloil, (ii) having a total solubility parameter from about 8.2 to about9.4, (iii) having a polar and hydrogen bonding solubility parameter fromabout 3.2 to about 4.3, (iv) having a non-polar solubility parameterfrom about 7.6 to about 8.4, (v) having a hydrogen bonding index numberfrom about 6.0 to about 12.0, and (vi) being substantially non-reactivewith said polyisocyanate prepolymer and said polyol.